1. Field
Aspects of one or more embodiments of the present invention relate to a laser crystallization system, a laser crystallization method, and a method of fabricating a display device.
2. Description of the Related Art
A substrate (having thin-film transistors (TFTs) formed thereon) is commonly used in active matrix displays. A TFT using a polycrystalline semiconductor film is capable of operating at high speed due to its high electron mobility, as compared to a TFT using an amorphous semiconductor film. Accordingly, research is being conducted on a technique of forming a semiconductor film with a crystalline structure by crystallizing an amorphous semiconductor film formed on an insulating substrate, such as a glass substrate.
For crystallization, a thermal annealing method using furnace annealing, a rapid annealing method, a laser annealing method, or a combination thereof may be used.
The laser annealing method, among other annealing methods, may apply high energy only to a certain area to be crystallized without causing excessive variations in the temperature of a substrate.
In general, pulse laser beams of an excimer laser are used in laser annealing.
However, it is difficult to form a uniform crystalline semiconductor layer by applying oscillated laser beams onto a non-uniform semiconductor layer. This problem may be associated with the application of laser beams with a non-uniform intensity to a semiconductor layer without consideration of the deposition thickness of the semiconductor layer.
Non-uniform crystallization, which leads to non-uniform resistance of TFTs, may contribute to product defects.
The application of laser beams in consideration of the thickness of a semiconductor layer requires a measuring process for identifying the deposition map of the semiconductor layer, which, however, increases the number of processes for forming TFTs and may, thus, result in an increase in tack time.